1. Field of the Invention
The field of the present invention is photonic devices capable of generating higher order harmonic emissions, particularly those photonic devices that do not mask the higher order harmonic emissions by other emission modalities.
2. Background
Various micro-cavity resonators have been utilized to re-circulate light and store optical power. In a typical micro-cavity resonator, light traverses around an interior surface of the cavity. The optical power stored in the resonator can be used in cavity quantum electrodynamics (cQED), photonics, and various optics applications. For example, U.S. Pat. No. 6,633,696 describes use of a micro-cavity resonator as an optical signal modulator.
The surface quality or finish usually affects the Q factor of the resonator, which is a measurement of the relationship between stored energy and the rate of dissipation of the energy. Resonators having both high Q factors and ultra-high Q factors are known in the art. For purposes of establishing a point of reference, a “high” Q factor is generally defined as a Q factor between about 104 up to about 106, and an “ultra-high” Q factor is generally defined as a Q factor greater than 106.
Surface-tension induced micro-cavities (STIM), such as droplets or micro-spheres, are examples of known high Q and ultra-high Q micro-cavities. Some STIMs, such as suspended liquid droplets, are known to have Q factors that approach 109. Such ultra-high Q STIMs, however, are typically confined to the laboratory as a result of the fabrication controls that are required to produce and maintain the spherical shape. For example, in the paper by Acker et al., “Third-order optical sum-frequency generation in micrometer-sized liquid droplets”, Optics Letters, Vol. 14, No. 8, p. 402 (Apr. 15, 1989), the disclosure of which is incorporated herein by reference, a liquid droplet of CCl4 was demonstrated to exhibit third order harmonic emissions when a pulsed laser beam having power output of about 0.5 GW is incident upon the droplet. The laser is required to have such a high power output due to poor optical coupling between the laser beam and the droplet. While the discovery of third harmonic emissions from a liquid droplet is of scientific interest, application of this discovery has been limited to liquid droplets. This is primarily because liquid droplets provide the advantage of forming a perfect, or nearly perfect, sphere due to the surface tension of the liquid, and the spherical shape creates inversion symmetry which suppresses second harmonic emissions, thereby enhancing the third harmonic emissions. Practical micro-cavity resonators which are capable of efficiently generating third harmonic emissions, however, remain elusive.
More recently, U.S. Patent Publication No. 20040179573, the disclosure of which is incorporated herein by reference in its entirety, discloses a micro-cavity resonator which is capable of both high Q and ultra-high Q factors. The technical advantage of this micro-cavity resonator is based on the fact that it can be fabricated with traditional wafer-based processing techniques and equipment, thus making it cost-efficient for use in various photonics applications in which high Q and ultra-high Q resonant cavities are desirable. However, because such micro-cavity resonators are a relative new discovery, the full usefulness and capabilities of these resonators have yet to be determined.